The present invention relates to a projection display apparatus and a display method using the projection display apparatus, achieving less persistence of vision for images to be displayed when beams are projected onto a screen via a projection unit even after undergoing optical modulation by an optical modulator of a relatively low response time based on input signals.
A display apparatus now widely used is a projection display apparatus equipped with liquid crystal display devices that optically modulate input light beams based on external input signals that carry video data, the modulated beams being enlarged and projected onto a screen, as disclosed in Japanese Unexamined Patent Application Publication No. 2007-003809 (referred to as Citation 1, hereinafter).
Such liquid crystal display devices are usually driven to switch frames depending on a frame frequency in such a way that, for example, at a frame frequency of 60 Hz, each frame is kept for 1/60 seconds before switched to the next frame.
Such a driving technique could, however, cause persistence of vision because a user recognizes an image now displayed and the next image when the next image is to be displayed. The persistence of vision often occurs when images to be displayed are rapidly moving images of something, such as, a specific kind of sports.
One technique to reduce the persistence of vision is disclosed in Japanese Unexamined Patent Application Publication No. 2003-186456 (referred to as Citation 2, hereinafter).
The liquid crystal display devices disclosed in Citation 2 are equipped with a mechanism of alternately and repeatedly displaying video images and black images by switching driving voltages to be applied to the liquid crystals and another mechanism of alternately displaying video images and black images at every second frame and at a frequency at least two times higher than a regular frame frequency.
However, the technique disclosed in Citation 2 requires switching circuitry for input or drive signals, which could make the liquid crystal display devices and/or projection display apparatus expensive. Moreover, the technique disdosed in Citation 2 divides a regular display period into at least two for displaying a black image, which thus not so advantageous for the liquid crystal display devices of a relatively low response time.
Moreover, when the technique of Citation 2 is applied to the projection display apparatus of Citation 1 in which a video image is enlarged when projected onto a screen, more persistence of vision could be caused for a projected video image, compared to a direct-view liquid crystal display apparatus.